AU601719B2 - A multistage tracking system - Google Patents

A multistage tracking system Download PDF

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Publication number
AU601719B2
AU601719B2 AU70056/87A AU7005687A AU601719B2 AU 601719 B2 AU601719 B2 AU 601719B2 AU 70056/87 A AU70056/87 A AU 70056/87A AU 7005687 A AU7005687 A AU 7005687A AU 601719 B2 AU601719 B2 AU 601719B2
Authority
AU
Australia
Prior art keywords
mirror
sled
drive coil
control amplifier
tilting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
AU70056/87A
Other versions
AU7005687A (en
Inventor
Ger L.M. Jansen
Piet J.M. Janssen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Laser Magnetic Storage International Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Laser Magnetic Storage International Inc filed Critical Laser Magnetic Storage International Inc
Publication of AU7005687A publication Critical patent/AU7005687A/en
Application granted granted Critical
Publication of AU601719B2 publication Critical patent/AU601719B2/en
Assigned to N.V. PHILIPS GLOEILAMPENFABRIEKEN reassignment N.V. PHILIPS GLOEILAMPENFABRIEKEN Alteration of Name(s) in Register under S187 Assignors: LASER MAGNETIC STORAGE INTERNATIONAL COMPANY
Assigned to PHILIPS ELECTRONICS N.V. reassignment PHILIPS ELECTRONICS N.V. Request to Amend Deed and Register Assignors: N.V. PHILIPS GLOEILAMPENFABRIEKEN
Anticipated expiration legal-status Critical
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
    • G11B7/08517—Methods for track change, selection or preliminary positioning by moving the head with tracking pull-in only
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/0857—Arrangements for mechanically moving the whole head
    • G11B7/08582—Sled-type positioners
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0901—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following only

Landscapes

  • Optical Recording Or Reproduction (AREA)
  • Burglar Alarm Systems (AREA)
  • Vehicle Body Suspensions (AREA)
  • Mechanical Optical Scanning Systems (AREA)
  • Moving Of The Head For Recording And Reproducing By Optical Means (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Optical Head (AREA)

Abstract

A multistage tracking system for an optical disk used in recording, storing and transmitting data and the like. The tracking system using a movable sled with objective lens for coarse tracking of individual tracks on the disk and a stationary tilting mirror providing fine tracking on a selected track.

Description

V
I
ORIGINAL
1 7 1 9 C CC c c C C f C C C This document contains they amendments made und'', Section 49 and is correct prining.
Igjt .rsj C wW-.4(f 3salw~t.. a'4St ns.Si COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1969 C CC CC C SC C e c c COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "A MULTISTAGE TRACKING SYSTEM" The following statement is a full description of this invention including the best method of performing it known to us:- -1- L7,m OSI-916 31-03- 1987 IlA A MULTISTAGE TRACKING SYSTEM BACKGROUND OF THE INVENTION This invention rel ates to a rotating disk tracking system and more particularly, but not by way of limitation, to a multistage tracking system for an optical disk.
Heretofore, multistage tracking system for an' optical disk used a fine tracking element on a movable part such as a slow moving sled, i.e. laser vision or a bulky sled such as a gas laser based optical data recorder. When using a slow moving sled most of the work done by the fine tracking element. The optical effects associated with large amplitude motion of the fine tracking element for instance vignetting, precludes positioning the mirror sled far from the objective lens. Therefore, it was found that the fine tracking element must be located on the sled.
When using a small high performance system, it is an advantage to have a stationary fine tracking element because high speed access requires a lightweight high band jiwidth sled. This requi res the sled to be capable of doing most of the work while tracking. The fine tracking element then will only have to move very slightly, thus avoiding the above-mentioned optical eftects. If the fine tracking element is on the sled, this will contribute to the mass and complexity of the sled thereby reducing it's response and consequently the element will have to do more of the 14 work than in the previous situation.
The above-mentioned problems related to a multistage tracking system for an optical disk has led to invention as described herein. In the following U.S.
Patents, U.S. Patent No. 4,225,873 to Winslow, RE 29,963 to Janssen, and U.S. Patent No. 3,829,622 to Elliot, optical systems are described having control systems with interacting loops and movable sleds witli articulating mirrors thereon. None of these pri or art patents particular point out the unique features and the advantages of the subject multistage tracking system as described herein.
0SI-916 31-03-1987 2 SUMMARY OF THE INVENTION The subject multistage tracking system provides a small high performance system with the advantage of a stationary tilting mirror removed from the movable sled, thereby providing high speed access ana coarse and fine tracking on an optical rotating disk.
The multistage tracking system provides a movable sled with objective lens for coarse tracking a desired track on the optical disk with a stationary tilting mirror providing fine tracking on the disk.
The multistage tracking system for a rotating optical disk includes a movable sled with a movable objective lens and fixed mirror. The sled is disposed Sbelow the tracks on the disk. The sled includes a sled drive means for moving the objective lens near a desired track. A stationary tilting mirror is disposed adjacent to the sled. The mirror has a mirror drive means for tilting the mirror for fine tracking. Optics is electrically connected to the stationary tilting mirror drive means and sled drive means and provides a light beam directed toward the tilting mirror. The tilting mirror reflects the light toward the fixed mirror below the objective lens and focuses the beam through the lens onto a desired track.
The optics provide an optically generated position signal to the mirror drive means and the sled drive means for coarse tracking and fine tracking on the rotating optical di sk.
The advantages and objects of the invention will become evident from the following detailed description of the drawings when read in connection with the accompanying drawings which illustrate preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a schematic of the multistage tracking system.
Fig. 2 illustrates an alternate embodiment of the multistage tracking system with parallel or series PHA 70042 3 29.6.90 driven actuator coils.
Figs. 3 and 4 illustrate frequency curves of the tilting mirror amplification and sled amplification.
Figs. 5 and 6 illustrate curves illustrating the resonance frequency of the tilting mirror and sled drive coil.
Fig. 7 and 7A illustrate electrical diagrams for series or parallel driven actuator coils.
DETAILED DESCRIPTION OF THE DRAWING In Fig. 1 the multistage tracking system is designated by general reference numeral 10. The system is used with a rotating optical disk 12 having a plurality of tracks 14 thereon. The disk 12 is rotated as indicated 44 by arrow 16. A movable sled 18 is positioned opposite to o,J 5 the tracks 14 and moves radially across the width of the tracks as indicated by arrow 20. The movable sled 18 includes an objective lens 22 disposed above a 45 degree 0 off fixed mirror 24. The sled 18 is moved radially by an electric motor connected to a drive coil 26. The motor is not shown in the drawings. While the electric motor and Q~l drive coils 26 are used to move the sled 18 for coarse tracking, it should be appreciated that various types of drive means could be used equally well.
A stationary tilting mirror 28 is disposed adjacent the disk 12 and is connected to an electric motor and a mirror drive coil 30. While the tilting mirror 28 is driven electrically it could also be driven by a variety of different drive means. A light beam indicated by dotted lines 32 is projected from optics 34. The beam 32 may be a 1J 30 parallel or collimated beam which is directed toward the degree stationary tilting mirror 28. The mirror 28 reflects the light toward the fixed 45 degree mirror 24 on the movable sled 18. The beam 32 is focused through the objective lens 22 onto a desired track 14 on the disk 12.
The tilting of the mirror 28 is indicated by arrow 29.
The multistage tracking system 10 incorporates two stages; a coarse tracking loop using the sled 18 and a I I
J
0 1 o I 0~~SI-916310-98 31-03-1987 0 fine tracking loop using the stationary tilting mirror 28.
The fine tracking loop consists of an optically generated position signal E-RAD which is fed through from the optics 34 via lead 35 to. a preamplifier 36 and to a fine control amplifier 38 via lead 39. The fine control amplifier 38 drives the drive coil 30 of the stationary tilting mirror 28.
The coarse tracking loop is fed using an angle error signal from the fine tracking mirror 28. The angle error signal can be obtained ,in two ways. One way is using an angle sensor 40 connected to the mirror 28 via lead 41.
When using the angle sensor 41, driving of the coarse loop can be independent of the characteristics of the fine tracking mirror. It is possible to use a mirror 28 with slide bearings and not be affected by the associated friction. The angle sensor 40 feeds the signal through a coarse control ampl ifier 42 via leads 43 and 45 to the sled drive coil 26. In the alternative and without using the angle sensor 40, the mirror needs to be spring suspended and the bandwidth of the coarse loop is limited by the resonance frequency of the fine tracking mirror 28. Below the resonance frequency the current frm the mirror drive coil 30 is proportional to the angle of the tilting mirror 28 and the signal is fed to the coarse control amplifier 42 via leads 47 and 43.
In Fig. 2 an alternate embodiment of the multistage tracking system 10 is shown using a control amplifier 48 rather than the fine control amplifier 38 and the coarse control amplifier 42. In this embodiment the control amplifier 48 feeds the two drive coils 30 and 26.
The low frequency part of the drive current is directed towards the sled drive coil 26 and the high frequency part of the current directed towards the mirror drive 30. The sled drive coil 26 has a higher inductance than the mirror drive coil 30. With the addition of a high-pass element Such as a capacitor 50 connected via lead 41 to the mirror drive coil 30 all the flow frequency current from the control amplifier 48 will be directed to the sled drive coil 26 via lead 53. The high frequency portion of the drive current will pass over the capacitor 50 to the mirror
I
OSI-916 31-03-1987 drive coil In Figs. 3 and 4, log gain of the controller is shown as a vertical line 54 and log frequency is shown as a horizontal line 56. The resonance indicated by line 58 of the tilting mirror 28 is set at a high frequency, for example a few kilohertz, and beyond the bandwidth of the fine tracking loop as shown in Figs. 1 and 2. Without using the angle sensor 40, the bandwidth of the coarse loop can approach the bandwidth of the fine tracking loop. In order to avoid vignetting of the light beam 32 only very small angles of the tilting mirror 28 are allowed. The bandwidth of the coarse system therefore, has to be very high. In Figs. 3, a dotted line 60 illustrates the lead required when driving the mirror beyond its resonance.
Fig. 4 illustrates the transferof the sled control amplifier indicated by line 62.
In Figs. 5 and 6 log gain is again shown as a vertical line 54 with log frequency shown as a horizontal line 56. In Fig. 5 line 64 illustrates the mirror loop gain with line 66 illustrating the sled loop gain. A total transfer of the mirror loop and sled loop is illustrated by a dotted line 68.
In Fig. 6 a controller transfer is indicated by line 70 with a vertical dotted line 72 representing a crossover total loop. Figs. 7, and 7A illustrate alternate circuiting for series or parallel drive actuator coils with Fig. 7 being a parallel wiring system and Fig. 7A being a alternate series drive circuit application.
From reviewing the above detailed description of the multistage tracking system 10, it can be .iY seen that the system applies high-pass filtering for fine mirror tracking that reduces excursions and thus avoids associated adverse optical efforts thereby providing improved coarse and fine tracking used in conjunction with optical recording disks and the like.
Changes may be made in the construction and arrangement of the parts or elements of the embodiments as desribed herein without departing from the spirit or scope of the invention defined in the following claims.
I.r. P--i ~i

Claims (3)

  1. 3. The system as described in Claim 2 further including a coarse control amplifier electrically wired between the mirror drive means and the sled drive means.
  2. 4. The system as described in Claim 3 further including an angle sensor wired between the mirror drive means and the coarse control amplifier. A multistage tracking system for a rotating optical recording disk, the system comprising: a movable sled with an objective lens and fixed degree mirror, the sled disposed below tracks on the disk, the sled having an electrically driven coil for moving the objective lens PHA-70042 7 29.6.90 below and near a desired track; a 45 degree stationary tilting mirror disposed adjacent the sled, the tilting mirror having an electrically driven mirror drive coil for tilting the mirror; and optic means electrically connected to the mirror drive coil and sled drive coil and providing a light beam~ directed toward the tilting mirror, the tilting mirror reflecting the light toward the fixed mirror next to the objective lens and focusing the beam through 6 0 the lens onto a desired track, the optical 00 a 0 means further providing an optical generated a a a 0.0 aposition signal to the mirror drive coil and V0o11 sled drive coil through a preamplif ier and a control amplifier. 64 6. The system as described in Claim 5 where the o 0 0*control amplifier provides a low frequency drive current directed toward the sled drive coil and a high frequency current directed toward the mirror drive coil. 0 7. The system as described in Claim 6 further 86E 1 0 44 including a capacitor wired between the control amplifier and the mirror drive coil.
  3. 8. A multistage tracking system substantially as described with reference to the accompanying drawings. DATED THIS TWENTY-NINTH DAY OF JUNE, 1990 LASER MAGNETIC STORAGE INTERNATIONAL COMPANY N-V
AU70056/87A 1986-03-17 1987-03-16 A multistage tracking system Expired AU601719B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US06/840,058 US4768180A (en) 1986-03-17 1986-03-17 Multistage tracking system
US840058 1986-03-17

Publications (2)

Publication Number Publication Date
AU7005687A AU7005687A (en) 1987-09-24
AU601719B2 true AU601719B2 (en) 1990-09-20

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AU70056/87A Expired AU601719B2 (en) 1986-03-17 1987-03-16 A multistage tracking system

Country Status (8)

Country Link
US (1) US4768180A (en)
EP (1) EP0238138B1 (en)
JP (1) JP2783405B2 (en)
KR (1) KR940011230B1 (en)
AT (1) ATE91558T1 (en)
AU (1) AU601719B2 (en)
CA (1) CA1263748A (en)
DE (1) DE3786473T2 (en)

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JP2593941B2 (en) * 1989-08-19 1997-03-26 富士通株式会社 Actuator offset removal device for optical disk drive
JP2861457B2 (en) * 1990-05-24 1999-02-24 セイコーエプソン株式会社 Optical recording / reproducing device
US5452276A (en) * 1991-01-31 1995-09-19 Deutsche Thomson-Brandt/Gmbh Tracking regulation circuit including apparatus for disabling coarse drive signals
US5446712A (en) * 1991-04-22 1995-08-29 Seiko Epson Corporation Optical system having a precision angular displacement mechanism including a flat metal spring
EP0574996B1 (en) * 1992-06-19 1997-09-03 Koninklijke Philips Electronics N.V. Device for optically scanning a surface
EP0574995B1 (en) * 1992-06-19 1998-01-21 Koninklijke Philips Electronics N.V. Device for optically scanning a surface
US5566152A (en) * 1992-10-21 1996-10-15 Matsushita Electric Industrial Co., Ltd. Tracking control system with correction capabilities for correcting disagreement between optical axes
DE19743935A1 (en) * 1997-10-04 1999-04-08 Thomson Brandt Gmbh Device for reading or writing to optical recording media

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Also Published As

Publication number Publication date
EP0238138B1 (en) 1993-07-14
KR940011230B1 (en) 1994-11-29
CA1263748A (en) 1989-12-05
EP0238138A2 (en) 1987-09-23
KR870009364A (en) 1987-10-26
EP0238138A3 (en) 1989-12-13
ATE91558T1 (en) 1993-07-15
DE3786473T2 (en) 1994-01-27
DE3786473D1 (en) 1993-08-19
AU7005687A (en) 1987-09-24
JP2783405B2 (en) 1998-08-06
JPS62275328A (en) 1987-11-30
US4768180A (en) 1988-08-30

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